The so-called “flip-chip bonding” in which electrodes of a semiconductor chip and electrodes on the signal read-out substrate face each other and are electrically connected to each other through conductive bumps (bump electrodes) has a structure as illustrated in FIG. 6. In FIG. 6, reference numeral 101 denotes a signal read-out substrate, reference numeral 102 denotes a semiconductor chip, reference numeral 103 denotes a pixel electrode, reference numeral 104 denotes a conductive bump, and reference numeral 105 denotes an insulating layer.
The signal read-out substrate 101 is a signal read-out substrate such as a CMOS integrated circuit in which the pixel electrodes 103 are arranged in a two-dimensional matrix shape. In addition, instead of the semiconductor chip, a substrate represented by a counter substrate or the like may be used. The pixel electrodes 103 are formed on the signal read-out substrate 101. The conductive bumps 104 are formed on the semiconductor chip 102 as counter pixel electrodes at positions facing the pixel electrodes 103.
The flip-chip bonding illustrated in FIG. 6 is used for a photodetector or a radiation detector to detect light or radiation and extract a signal obtained by detection. In addition, besides a metal bonding method using a solder bump, a gold bump, or the like, the flip-chip bonding may also include an adhesive bonding method such as conductive resin bonding which is bonding using an organic material or anisotropic conductive member bonding. Besides the flip-chip bonding, the invention can also be applied to cases where both substrates are used for bonding.
In addition, the semiconductor chip or the substrate that detects light or radiation has a photoelectric conversion semiconductor layer. The semiconductor chip or the substrate has a common electrode for applying a bias voltage to the incident side of light or radiation and is configured such that the photoelectric conversion semiconductor layer is interposed between the common electrode and the pixel electrode described above (refer to, for example, Patent Document 1).
In the case of forming the bump electrode on the counter pixel electrode, in metal bonding using a gold bump or the like, by applying pressure, energy such as heat, ultrasonic wave, or the like to the bonding surface between the bump electrode and the pixel electrode, or by using a pressing method of bonding by interdiffusion of metals between a bump material and an electrode material, bonding with high strength and reliability is obtained. As the bump material and the electrode material, Au (gold) as described above which is physically and chemically stable and has an appropriate diffusion coefficient is used.
Patent Document 1: JP-A-2001-177141